Carrier and clip each having sinterable, solidified paste for connection to a semiconductor element, corresponding sintering paste, and corresponding production method and use

1. Field of the Invention

The invention relates to a carrier for at least one semiconductor element, which carrier has at least one functional surface for connection to the semiconductor element. The invention furthermore relates to a clip for at least one semiconductor element, which clip has at least one functional surface for connection to the semiconductor element. The invention furthermore relates to a method for producing such a carrier or such a clip, as well as to the use of the carrier or clip and to a sintering paste.

2. Discussion of the Related Art

A carrier of the type mentioned in the introduction is known, for example, from DE 10 2009 017 853 A1. During the production of the known carrier, the sintering paste is initially applied onto the lower side of the semiconductor element. The semiconductor element is then brought into contact with the functional surface of the carrier and temporarily fixed. The actual connection is then carried out by sintering the carrier to the semiconductor element using the paste. In this way, a layer system that is processed further as a semiconductor component is produced.

The carrier may, for example, be a so-called lead frame, and the semiconductor element may be a chip.

In the known method, the sintering material, or solder, is applied in a separate process. Specifically, the use of solder is expensive and increases the process and material costs.

The object of the invention is to provide a carrier or clip respectively for a semiconductor element, which in each case simplifies the production of a semiconductor component. The object of the invention is furthermore to provide a production method for such a carrier or clip, as well as a use and a sintering paste.

The invention is based on the concept of providing a carrier for at least one semiconductor element, which carrier has at least one functional surface for connection to the semiconductor element. According to the invention, the material of the carrier comprises a metal. A layer of a sinterable solidified paste, which contains silver and/or a silver compound and 0.1%-2% fatty acids or organic binder, is arranged on the functional surface. The carrier and the layer forming an intermediate product which can be connected to the semiconductor element.

The solidified paste contains silver and/or a silver compound. The paste furthermore contains 0.1%-2% fatty acids or organic binder. In other words, besides silver and/or a silver compound, the paste additionally contains 0.1%-2% fatty acids or organic binder. The solidified paste contains silver and/or a silver compound as well as 0.1%-2% fatty acids or organic binder.

The fatty acids may, for example, be caprylic acid (octanoic acid) and/or capric acid (decanoic acid) and/or lauric acid (dodecanoic acid) and/or myristic acid (tetradecanoic acid) and/or palmitic acid (hexadecanoic acid) and/or margaric acid (heptadecanoic acid) and/or stearic acid (octadecanoic acid) and/or arachidic acid (eicosanoic acid) and/or behenic acid (docosanoic acid) and/or lignoceric acid (tetracosanoic acid). The solidified paste preferably contains caprylic acid (octanoic acid) and/or lauric acid (dodecanoic acid) and/or myristic acid (tetradecanoic acid) and/or palmitic acid (hexadecanoic acid) and/or margaric acid (heptadecanoic acid) and/or stearic acid (octadecanoic acid).

The organic binder is preferably a polymer such as cellulose derivatives, for example methyl cellulose and/or ethyl cellulose and/or ethyl methyl cellulose and/or carboxymethylcellulose and/or hydroxypropyl cellulose.

The invention has the advantage that the carrier and the layer can be produced together, and they form a sinterable intermediate product. The sinterable intermediate product may be used by a further manufacturer in order to equip the carrier with the semiconductor element, so that only the connection by sintering between the carrier and the semiconductor element is then carried out. It has been found that it is less expensive for the carrier, or the lead frame, to be produced together with the sinterable layer and then subsequently connected to the semiconductor element.

With the layer formed from the sinterable solidified paste the carrier forms an intermediate product which can be handled separately and can be processed further in a temporally or spatially separate process.

Preferably, the carrier has at least one terminal, a further layer of a sinterable solidified paste, which contains silver and/or a silver compound and 0.1%-2% fatty acids or organic binder being arranged on the terminal on the side of the functional surface. The layer can be connected to a clip, in particular a clip as claimed in claim 5 . This embodiment has the advantage that not only the functional surface, but in one working step also the terminal or a plurality of terminals can be provided with the sinterable layer, so that the production process is simplified further.

It has proven advantageous for the thickness of the layer to be from 5 μm to 100 μm, in particular from 5 μm to 50 μm.

The layer may contain silver particles having a particle size of from 200 nm to 20 μm.

In the scope of the invention, a clip for connection to a semiconductor element and a carrier is disclosed and claimed. The clip has the same features as the carrier, i.e. at least one functional surface for connection to the semiconductor element, the material of the clip comprising a metal. A layer of a sinterable solidified paste, which contains silver and/or a silver compound and 0.1%-2% fatty acids or organic binder, is arranged on the functional surface. The clip and the layer form an intermediate product which can be connected to the semiconductor element. The advantages explained in connection with the carrier also apply for the clip.

The paste contains silver and/or a silver compound. The paste furthermore contains 0.1%-2% fatty acids or organic binder. In other words, besides silver and/or a silver compound, the paste additionally contains 0.1%-2% fatty acids or organic binder. The solidified paste contains silver and/or a silver compound as well as 0.1%-2% fatty acids or organic binder.

The fatty acids may, for example, be caprylic acid (octanoic acid) and/or capric acid (decanoic acid) and/or lauric acid (dodecanoic acid) and/or myristic acid (tetradecanoic acid) and/or palmitic acid (hexadecanoic acid) and/or margaric acid (heptadecanoic acid) and/or stearic acid (octadecanoic acid) and/or arachidic acid (eicosanoic acid) and/or behenic acid (docosanoic acid) and/or lignoceric acid (tetracosanoic acid). The solidified paste preferably contains caprylic acid (octanoic acid) and/or lauric acid (dodecanoic acid) and/or myristic acid (tetradecanoic acid) and/or palmitic acid (hexadecanoic acid) and/or margaric acid (heptadecanoic acid) and/or stearic acid (octadecanoic acid).

The organic binder is preferably a polymer such as cellulose derivatives, for example methyl cellulose and/or ethyl cellulose and/or ethyl methyl cellulose and/or carboxymethylcellulose and/or hydroxypropyl cellulose.

Regarding the advantages of the embodiments of the clip, reference is made to the advantages disclosed and described in connection with the carrier.

The method according to the invention for producing the carrier for at least one semiconductor element, or the clip for connection to a semiconductor element, is based on the carrier or the clip being structured, in particular stamped, and having a functional surface for connection to the semiconductor element. A sintering paste, in particular a sintering paste containing silver, is applied onto the functional surface, and is heated for drying and solidification. As a result, a solidified and sinterable layer is formed on the functional surface of the carrier or clip. The intermediate product produced in this way is connected to the semiconductor element in a separate process.

Preferably, the functional surface is coated with a bonding agent, in particular with silver or a silver compound, before the sintering paste is applied. The sintering paste may be applied by a template printing method, in particular by a spraying method or a dispensing method.

Furthermore, the use of the carrier is disclosed and claimed in the scope of the invention. In addition, a sintering paste for application onto a carrier and/or onto a clip is disclosed and claimed, which is distinguished in that it can be applied onto the carrier.

The invention will be explained in more detail below with the aid of an exemplary embodiment with reference to the appended drawings, in which:

FIG. 1 shows a side view of a carrier or lead frame with an applied layer;

FIG. 2 shows a side view of a clip with an applied sinterable layer; and

FIG. 3 shows a semiconductor component with a lead frame and a clip according to FIGS. 1, 2 .

FIG. 1 shows a side view of a carrier or lead frame according to an exemplary embodiment according to the invention. The carrier is a stamped or etched part, which is produced by methods known per se. The carrier forms an intermediate product, which is connected to a semiconductor element, for example a chip, in a further separate method step. To this end, the carrier has a functional surface 10 , on which the semiconductor element is placed. In order to connect the semiconductor element to the functional surface 10 of the carrier, a layer 12 which consists of a sinterable solidified paste is applied onto the functional surface 10 . The layer 12 contains silver and/or a silver compound and 0.1%-0.2% fatty acids or organic binder.

In order to produce the layer 12 , a sintering paste is applied onto the functional surface 10 in a preliminary process. The sintering paste is then dried. Liquid constituents are in this case removed at room temperature. The solidification, i.e. the drying of the paste, is carried out in such a way that full sintering of the paste does not occur. For this reason, the solidified paste, or the layer 12 , has a residual reactivity for the sintering process subsequently carried out.

The drying of the paste is preferably carried out at a temperature, a pressure, an air humidity and for a time which are suitable for removing the solvents from the paste to the greatest possible extent, but without the sintering process already having fully taken place inside the paste after the drying. The drying may for example be carried out at temperatures below 200° C. and more preferably below 150° C., for example at about 120° C. for a time of preferably 3-60 minutes. Conventional drying apparatuses may be used for the drying.

The carrier with the layer 12 according to FIG. 1 therefore forms a preform, which is supplied as an intermediate product to the further production process, for example by another manufacturer. The intermediate product is stable overall, and can be handled in such a way that it can be transported for the further processing. This is because the originally wet sintering paste is solidified and is then geometrically stable at ambient temperature.

The C—Ag ratio of the layer lies in the range of C:Ag=1/1000-2/100. The particle size of the silver particles contained in the layer is from 200 nm to 20 μm.

FIG. 2 represents a clip which, like the carrier according to FIG. 1 , is provided with a solidified sinterable paste, or a corresponding layer 12 . For the construction and production of the clip, reference is made to the comments in connection with FIG. 1 .

FIG. 3 shows the lead frame package after processing. In other words, the lead frame according to FIG. 1 and the clip according to FIG. 2 are respectively processed further as an intermediate product to form the package according to FIG. 3 , specifically in a separate step. To this end, the clip according to FIG. 3 is connected and sintered to the lead frame and the clip in the manner shown in FIG. 3 .

Sintering is intended to mean the connection of two components by heating while circumventing the liquid phase.

In FIG. 3 , it can furthermore be seen that the lead frame has at least one terminal, which is connected to a corresponding terminal of the clip. The invention is carried out using a solidified sintering paste, which is applied as in the case of the intermediate products according to FIGS. 1, 2 . In this case, the sintering paste or the solidified layer 12 may be applied either on the terminal 11 of the lead frame or on the terminal 11 of the clip, and thus form a part of the respective intermediate product. The layer arrangement consisting of the clip, chip or semiconductor element and lead frame or carrier is encapsulated in a further step with a so-called mold compound, so that the complete lead package is produced.

The invention, and the exemplary embodiments described above, have the advantage that the process and material costs are reduced.